ASC

DTC U0401: Engine malfunction detected

CAUTION:
^ If there is any problem in the CAN bus lines, an incorrect diagnostic trouble code may be set. Prior to this diagnosis, diagnose the CAN bus lines.
^ If diagnostic trouble code U0401 is set in ASC-ECU, always diagnose the CAN bus line. If there is any fault in the CAN bus lines, an incorrect diagnostic trouble code may be set. In this case, the set diagnostic trouble code is not highly reliable.
^ Before replacing the ECU, ensure that the communication circuit is normal.

CIRCUIT OPERATION
Engine-related signals are sent or received to and from between ASC-ECU and engine ECU via CAN bus lines.

DTC SET CONDITIONS
This diagnostic trouble code is set when the engine ECU malfunction has been detected.

PROBABLE CAUSES
^ Malfunction of engine system
^ Engine ECU malfunction
^ ASC-ECU malfunction
^ External noise interference

DIAGNOSIS

Required Special Tools:
^ MB991958 Scan Tool (M.U.T.-III Sub Assembly)
^ MB991824: Vehicle Communication Interface (V.C.I.)
^ MB991827 M.U.T.-III USB Cable
^ MB991910 M.U.T.-III Main Harness

STEP 1. M.U.T.-III CAN bus diagnostics
Use scan tool to diagnose the CAN bus lines.
Q: Is the check result normal?
YES: Go to Step 2.
NO: Repair the CAN bus lines. On completion, go to Step 5.

STEP 2. M.U.T.-III diagnostic trouble code
Use scan tool to check that any diagnostic trouble code other than the code U0401 is set in ASC-ECU.
Q: Is any DTC set?
YES: Troubleshoot the relevant diagnostic trouble code, and then go to Step 5.
NO: Go to Step 3.

STEP 3. M.U.T.-III other system diagnostic trouble code
Use scan tool to check that the diagnostic trouble code is set by the engine ECU.
Q: Is any DTC set?
YES: Troubleshoot the relevant diagnostic trouble code, and then go to Step 5.
NO: Go to Step 4.

STEP 4. Check whether the diagnostic trouble code is reset.
Q: Is DTC U0401 set?
YES: Replace the ASC-ECU, and then go to Step 5.
NO: Intermittent malfunction.

STEP 5. Check whether the diagnostic trouble code is reset.
Q: Is DTC U0401 set?
YES: Return to Step 1.
NO: The procedure is complete.